Delay-Aware Energy Optimization for Flooding in Duty-Cycled Wireless Sensor Networks

Flooding, by which the sink node broadcasts messages to the entire network, is an important and common operation in wireless sensor networks (WSNs). The emerging synchronous duty-cycled wakeup schedules together with the unreliable communication of WSNs post new challenges for efficient broadcast protocol design, and the existing methods are not appropriate to address this problem. This paper proposes a delay-aware energy-optimized flooding algorithm (DEF) tailored for synchronous duty-cycled WSNs, which can act as an enhanced scheme for most flooding trees. DEF globally adjusts a constructed flooding tree, to maximize the energy efficiency improvement while following the delay constraint. To this end, we first remodel the flooding problem in the new context mathematically. Then, we introduce a routing metric, which fully utilizes the features of synchronous duty-cycled WSNs for energy optimization, and design an effective delay-aware tree adjusting approach. Extensive evaluation results demonstrate that DEF could save considerable energy, while the flooding delay keeps unchanged or even decreases slightly. In addition, a modified minimum spanning tree (MMST) is proposed to indicate the approximate energy lower bound. Compared with MMST, DEF achieves comparable energy efficiency and better latency performance.